1. Field of the Invention
The present invention relates to a toothed-belt fixing mechanism. As employed herein, the terms "fixing" or "to fix" indicate both the case where one end portion of the toothed-belt is fixed and the case where both end portions of the toothed-belt are connected with each other to form an endless belt.
2. Description of the Prior Art
The toothed-belt has been used in various types of movable member-driving apparatus requiring an appointed timing, such as an optical system-driving apparatus in an optical system travel type copying machine, a printing head-driving apparatus in a printer, a driving apparatus of an automatic door and a travelling-driving apparatus of a robot car truck.
When one end portion of such a toothed-belt is fixed, as shown in FIG. 9, an end portion of a toothed-belt (a) is positioned between an uneven plate (b) having a plurality of teeth engaging with teeth of belt (a) and a flat plate (c) and is fixedly mounted on a stationary portion or member (e), such as the body of a copying machine, by means of screws (d) passing through members (a), (b), (c).
The above described conventional toothed-belt has the following problems.
That is to say, when the toothed-belt (a) is fixed, it is necessary that it be fixed under tension. However, with such known fixing method it has been shown to be remarkably difficult to fix the toothed-belt (a) under an appropriate tension.
Accordingly, in the case of, for example, an apparatus such as an optical system-driving apparatus in a large-sized optical system travel type copying machine, in which a central movable member is driven by means of a pair of toothed-belts disposed on opposite sides of the movable member, it is difficult to balance the tensions on such two oppositely positioned toothed-belts. As a result, the movable member is not capable of moving smoothly during various operating circumstances.
In addition, in a case where it is necessary to regulate the tension on the belt due to extension of the belt, the regulating operation also is difficult.
On the other hand, for example, in the production of a long endless toothed-belt such as an endless toothed-belt used in a driving apparatus of an automatic door, opposite end portions of the toothed-belt are connected with each other to form an endless belt.
In such a case as shown in FIG. 10, opposite end portions of a toothed-belt (a) are positioned between an uneven plate (b) provided with teeth engaging with teeth of belt (a) and a flat plate (c) and are fixed by tightening of bolts (d) passing through members (a), (b) and (c) and nuts (f). Thereby, opposite end portions of the toothed-belt (a) are connected with each other, thereby forming an endless belt.
The above described conventional arrangement has the following problems.
That is to say, in a case where a distance between axes of pulleys over which passes the endless toothed-belt is constant, when opposite end portions of the toothed-belt (a) are connected with each other to form the endless belt, such connection is carried out under a condition that some tension is imparted to the belt (a). However, in the above described connecting method, it is very difficult to achieve connection while the toothed-belt (a) is being pulled by a constant force. Furthermore, since the toothed-belt (a) is pulled by a pitch of the teeth at a time, the tension is imparted stepwise, such that fine regulation of the tension is impossible.